1. Field of the Invention
This invention relates to a roll for use under high or low temperature conditions; for example conveyor rolls such as those used in a flat glass annealing lehr. The roll has at least one tire member with a frusto-conical surface which engages against a matching frusto-conical surface of a retaining member, and the tire member is of a different material from the retaining member.
Such rolls usually have annular tires which project from a central shaft. Under some temperature conditions, for example when transporting flat glass after it has been annealed, a range of materials are available for the tires, and a resilient material, for example rubber, can be selected which, because of its resilience, accommodates differential thermal expansion between the shaft of the roll and the tires mounted on the shaft. When designing rolls for operation under high temperature conditions, for example up to temperatures of the order of 650.degree. C. a rigid tire material is usually necessary and this gives rise to problems due to differential expansion as between the shaft of the roll and the tires when any change in temperature takes place for example during warming-up of the lehr or when a hot roll in a lehr has to be changed.
2. Description of the Prior Art
A roll for hot or cold rolling is known from United Kingdom Pat. No. 1,374,130, in which a ring of hard metal alloy mainly consisting of hard carbides, is inset into the wall of a steel roll. The ring has frusto-conical faces and the roll body is cast into the ring, and the ring is compressively stressed as the cast roll body cools.
If the material of the shaft, in a roll of known construction, has a greater coefficient of thermal expansion than the material of the tire, the shaft will expand more than the tire as the temperature of the roll increases and the tire may be subjected to undesirable stress which may be sufficient to rupture the tire. If the coefficient of thermal expansion of the material of the shaft is less than the coefficient of thermal expansion of the material of the tire, the tire will expand more than the shaft and will tend to become detached from the shaft.
This problem has been alleviated to a degree, in the past, by designing the roll so that the parts of the roll have dimensions at the particular temperature of use such that any stress to which the tire is subjected has an acceptable value. This however can impose the need fo effecting adjustment after the roll has been assembled in the workshop at room temperature and during its heating up to the temperature of use. Further this usually limits the temperature of use to the particular temperature for which the roll is designed or, at best, a narrow temperature range around that particular temperature. It is a main object of the present invention to solve the problem of how to design a roll having one or more projecting tires spaced apart along the roll, which roll is suitable for use under hot or cold conditions.